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CRAZY ATF change out method?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Can Can, Mar 22, 2001.

  1. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    I was in the local parts store today looking at a bigger better aux. tranny cooler today when a crazy idea hit me.........

    When you do your tranny filter and replace the fluid, you only change out about 30% of your ATF. I was thinking about a way of getting ALL the ATF replaced, kind of like the way the lube shops can circulate new fluid through the tranny until all the old stuff is removed.

    Is it possible to unhook both lines from your tranny cooler, start the truck, and let the tranny pump suck clean flud into the system(out of a gallon jug, for example)through the intake line, while it spits the used fluid into another jug? You could do this with 3 or four gallons in a row until only fresh ATF was coming out.

    Am I on crack(Grim?.......teehee) or could this possibly work? Is there enough suction from the tranny pump for this to happen?

    Just another crazy idea..............eh?


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  2. dyeager535

    dyeager535 1 ton status Premium Member

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    I'm not positive that the fluid BACK to the radiator is "sucked" back in, or forced by the incoming fluid...if it is sucked in, then that should be no problem.

    Dorian
    My K5 and Chev/Olds tech/links page: <A target="_blank" HREF=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</A>
     
  3. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    So you think you'd have to pressurize the incoming fluid to get it through the system? I always thought that a tranny had an internal pump that was two stage, as in push AND pull?

    I just assumed this.............I don't know dick about the inside of a tranny..........



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  4. Chris Demartini

    Chris Demartini 1/2 ton status

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    <font color=blue>Disconnect the hose that goes into the radiator and have someone hold it in a catch pan. Run the engine in N (this will still turn the foward pump) until fluid stops coming out then shut it down imediatly.</font color=blue>

    [​IMG]
     
  5. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    So the pump is only a pusher? I guess you could empty the whole system and then just refill it a litre at a time through the dipstick/filler tube. How many litres will a 700r4 with a big aux. tranny cooler take?

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  6. 90K5

    90K5 1/2 ton status

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    10-11 qts.

    90K5

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  7. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    That's how a lot of these shops actully do the swap but they have to presurize what's going back in. Not sure that just using it to pump the old fluid out will get it all out. The pump is driven by the converter and once the pump stops picking up fluid the converter may not pump out without having more pumped in. It will keep the fluid in the converter because of the centrifical force of it spinning. The vast majority of the fluid is in the converter not the pan. As I recall the first place the ATF goes after coming out of the pump is to the cooler.

    Diging it in the dirt with my K5's
    Grim-Reaper
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  8. jarheadk5

    jarheadk5 1/2 ton status

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    I talked to the guy who powerflushed my tranny when I had it done. He said the machine he uses actually pumps fresh fluid into the tranny to ensure the nasty stuff gets purged from everywhere. He also said, as Grim said, some places just crack a line and let the tranny pump itself "dry", then refill and call that flushed.

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  9. Twiz

    Twiz 1/2 ton status

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    Pump -it- dry, yikes does that scare anyone but me? I;m not a tranny guy but I think the pump sucks fluid from the pan and pushes it,
    \
    Sorry, reread that, opps



    <P ID="edit"><FONT SIZE=-1>Edited by Twiztid on 03/22/01 09:21 PM (server time).</FONT></P>
     
  10. jarheadk5

    jarheadk5 1/2 ton status

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    No, I don't like the idea of the pump running dry either. I've seen and heard what running a hydraulic pump dry can do to it, and it's not pretty.

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  11. wayne

    wayne 3/4 ton status

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    A guy I know owns a tranny shop and he puts a small drain plug in the converter when he services them.

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  12. CaptCrunch

    CaptCrunch 1/2 ton status

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    The pump sucks fluid from the pan....if there is no fluid in the pan it will be dry. It won't suck up through the line. Don't try bleeding it dry... ever seen a car w/ a filter(which acts as the pickup for the pump) that has fallen off???? Can you say BOOM! Tranny will be toast quicker then heck because by the time you get no fluid coming out the pump will have been pumping for a bit. Overall it may work... but why screw with it??? If you really want it done good drop the pan and filter and change the fluid and then take it and hook it to a T-tech machine and have the fluid pushed through... yeah t-tech service is about $75 or so and the filter and fluid would be about $20... but $100 shelled out is a lot better then playing w/ fire and risking tranny failure.

    [​IMG]
    1987 Chevy K5 Blazer- 350 TBI
     
  13. dyeager535

    dyeager535 1 ton status Premium Member

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    You CAN, and I have, put a funnel on the dipstick fill tube, and just pour it in as it pumps out. I do think you'd be playing with fire with this method though. The funnel typically doesn't allow fluid to drain through very fast.

    Dorian
    My K5 and Chev/Olds tech/links page: <A target="_blank" HREF=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</A>
     
  14. jarheadk5

    jarheadk5 1/2 ton status

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    With the sensitivity and repair cost of a 700R4, I'd rather pay someone $100 and have it done RIGHT. Then again, it helps that the guy I used has been the "family mechanic" on my stepfather's side for like 30+ years.

    [​IMG] Semper Maintenance!
     
  15. dyeager535

    dyeager535 1 ton status Premium Member

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    I'd like to say that paying someone to do something on a vehicle means that about 50% of the time, you will have a problem that they caused or didn't fix when you drive away : ) Its a rare case when you can trust someone that works on auto's, BESIDES yourself. (which is why I do everything myself)

    Dorian
    My K5 and Chev/Olds tech/links page: <A target="_blank" HREF=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</A>
     
  16. KrebsATM02

    KrebsATM02 1/2 ton status

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    Hey with all this tranny talk i think i'm going to install my cooler this weekend. Which line is the intake and which one is the output. Thanks guys. Later Doug

    Doug Krebs
     
  17. Wheels

    Wheels 1/2 ton status

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    On 700R4 and TH350 the top line on the tranny is the return line and the bottom is the pressure. Follow this up to the radiator to determine which is the return line. Hook the cooler up on the return line (let it go through the radiator first).
     
  18. Twiz

    Twiz 1/2 ton status

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    O.K. I should have been clearer with my responce. DO NOT DO THIS!!!! The fluid moves through the cooler then through the rest of the trans and washes back into the pan, If you disconnnect the line and let it pump out, the trans will not get any fluid to lubricate it, and you WILL smoke the clutches. Think about it, you know the pan just catches the hot trans fluid after it has done it's job, then the pump sucks it from the pan and pushes the hot fluid to the cooler, the cool trans fluid then goes back to the trans to cool and lubricate. To check fluid flow, drive it for a little while then check the cooler line temp by hand (caution-surface is hot, don't sue me), the hot line is in and cold line is out. Also every thing that goes throught the radiator useually flows from the hot side to the cool side, so the hose to the water pump is cold, the hose from the t-stat is hot.

    Hope this was in time!
    Twiztid
     
  19. Blazer79

    Blazer79 1/2 ton status

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    Anybody know (or tried) if there's a way of draining the old oil by using a compressor and an air line. I think it would be safer because the engine is not turning, but I don't know if this is safe on the tranny internals. I was thinking if someone just hooks the air somewhere and watch all the old oil come out until there's no more, then close everything and pour new atf. Does this make sense?

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